Burglar-alarm



D. E. McDOUGALL.

Burglar Alarm.

Patented June 20, 1854.

u. PETERS. Phnlo-Ldhagnphar, Wnnhinglnn, u. c,

vNI D TA PATENT D E. MoDOUGALL, F SPRINGFIELD, MASSACHUSETTS.

BunGLAR-A AR Specification of Lettersli 'atent No. 1 1,1e dated June 20, 1854.

To all whom it may concern:

Be it knownthat" I, D. E. lVIGDOUGALL,

of Springfield, in the county of Hampden and State of: Massachusetts, have invented a new and improved implement for sounding an alarm when a door or window is tried or attempted to be forced open,

and which implement I designate a burglar-alarm; and Ido hereby. declare that the following is a full, clear, and. exact de scription of the construction and operation of the same, reference being had to the accompanying drawings, making a part of this specification, in which- Figure 1, is a side view of the implement applied to a door. Fig. 2, is a plan or top view of the same.

Similar letters of reference indicate corresponding parts in each of the two figures.

The nature of my invention consists in attaching to a door or window a fastener of peculiar construction, and a hammer, dog,.

and spring, so arranged that the hammer will be liberated and thrown down upon a percussion-cap, by the action of the spring, when the door or window'is tried or an attempt is made to open it.

To enable others skilled in the art to make and use my invention, I will proceed to describe its construction and operation.

A, represents a plate, having on its under side or surface a number of small spikes or spurs, (a). On one end of the upper side of the plate, A, are two ears, (6), (b), between which oneendof a brace, B, is secured by a pivot, (0). The opposite end of the brace is secured by a pivot, ((Z), to a vertical clamp, C. To the upper part of the clamp, C, there is secured by a pivot, (e), a guard, D, the lower end of which guard has a set screw, E, passing through it, the lower end of the set screw resting upon the upper surface of the brace, B, as clearly shown in Fig. 1. The ends of the guard and brace which are secured to the clamp, C, by the pivots, (e), ((Z) ,are slotted, and a ledge or rib, (f), on the clamp, C, fits in the slots. The back ends of the slots are inclined, as shown by the dotted lines, (g), in Fig. 1, and consequently the outer ends of both the guard and brace are prevented from rising beyond a certain height.

On one side of the brace, B, there is a hammer, F, secured to the brace by a screw or pivot, (h). The hammer is constructed in'the usual manner, or similar to those on gun-locks.

v G, is a spring, also secured to the brace. The longest end; of this spring fits in a recess, (z'), in the back side of the hammer and near its lower end, as is seen in Fig. 1.

.H, is a dog, attached to the brace by a screw or .pivot, (j), seen in Fig. 1. The lower end of this dog,wh'en the hammer is cocked catches against a small projection, (is), on. the back side of the hammer, as shown in Fig. 1. On the uper end of the dog, H, thereis an eye or socket, I, through which a rod, J, passes. The rod, J, has a nut, (Z), upon it, which bears against the eye or socket, and the outer end of the rod bears against the door, K.

L, is: a nipple attached to the brace, B, in such a position as to receive the blowof the hammer, F, when it descends. The nipple, L, communicates with a small barrel, M, more clearly seen in Fig. 2.

The implement is applied to a door in the following manner :The clamp, O, is placed against the lower part of the door, K, a

small ledge or projection, (m), on the lower end of the clamp being underneath the door, as shown in Fig. 1. The plate, A, is then hammered or pressed down to the floor, the

described, the hammer, F, is drawn back and cocked, the lower end of the dog, H, catching against the projection, (72), on the hammer and being kept on it by a small spring, (a), which bears against the dog. The rod, J, is then placed in the eyeor socket, I, on the upper part of the dog, the nut (Z), bearing against the eye or socket and the outer end of the rod against the door, K. A correct idea oftheposition of the several parts, when the hammer is cooked, will be obtained by referring to Fig. 1. When the door is tried, or an attempt is made to open it, the vibration of the door, acting upon the rod, J, will throw the lower end of the dog, H, off from the projection (is), on the hammer, F, and the main spring, Gr,

will force the hammer down upon the cap on the nipple, L, and explode it, thus creating the necessary alarm.

The barrel, M, may be added to the nipple or not, as desired. If it be thought that the explosion of a cap would not be sufficiently loud, the barrel, M, maybe attached and charged with a small amount of gun-v powder. In large houses this may be requisite; otherwise the ordinary percussion cap alone would probably answer. Thus it will be seen that the door is not only prevented from being forced open, but an alarm is also sounded when an attempt is made to force open the door.

The above implement may be applied to a window as well as to a door by securing the plate, A, to the frame of the window and the clamp, O, to the upper cross-piece of the sash.

The arrangement of the clamp, brace, guard, and plate for securing doors and windows being already patented by me, May 31st, 1853, I do not therefore claim the said device of the clamp, brace, guard, and plate for the above purpose; but

What I do claim as new, and desire to secure by Letters-Patent, is

The clamp, C, brace, B, and guard, D, and

plate, A, in combination with the hammer, F, the spring, G, and dog, H; the above parts being constructed and arranged in the manner and for the purpose substantially as set forth.

DUNCAN E. MODOUGALL.

Vitnesses:

J ONAH HOOKER, W. ARNOLD. 

